signEs256 method
Signs a JOSE signing input (base64url(header).base64url(payload)) and
returns the signature as raw R‖S (64 bytes), base64url — the ES256
wire format. A hardware implementation triggers the biometric/PIN gate
here when the key is auth-required.
Implementation
@override
Future<String> signEs256(String signingInput) async =>
b64uEncode(signBytes(utf8.encode(signingInput)));